This invention relates to winches having a powered rotatable drum for winding in and releasing a cable or the like and more particularly to a winch system of the type in which the drum is driven and controlled by means of fluid pressure-operated clutches and brakes.
Prior copending application Ser. No. 334,354 of L. F. Yates et al, filed Feb. 21, 1973 for "WINCH WITH FREE-WHEELING DRUM" and assigned to the assignee of the present application, discloses a winch assembly which is driven by an engine through a drive train having a normally disengaged input clutch which engages in response to fluid pressure to reel in cable. The drive train also includes a normally engaged brake for immobilizing the winch drum but which releases in response to fluid pressure in other modes of operation. In addition to the Brake-On and Reel-In modes of operation, the brake alone may be pressurized to effect a Brake-Off mode in which load forces pulling on the line may unwind cable against the limited resistance created by the drag of the drive train components. This limited resistance prevents excess unwinding of a cable by a load, from drum momentum or other causes, but is sufficiently strong that it is difficult or impossible to withdraw cable manually while such resistance is present. Accordingly, the drive train connects to the winch drum itself through a disconnect clutch which is normally engaged but which may be disengaged by fluid pressure to allow manual unreeling of cable from the drum without working against a substantial resistance. This form of winch assembly is highly useful on a log skidder vehicle, for example, which is used to drag logs from the site of a lumbering operation and also has substantial advantages in other contexts.
Prior U.S. Pat. No. 3,841,608 discloses a hydraulic control system for a winch assembly of this kind in which a manually operated control valve may be shifted between a series of positions to pressurize and depressurize appropriate ones of the clutches and brake of the drive train in order to accomplish the several operational modes described above. The valve settings include Reel-In, Brake-On, Brake-Off and Free-Spool and are realized by movement of a control lever or the like. For safety reasons as well as for convenience of operation, centering springs urge the control valve towards the Brake-On position so that if the operator releases his control lever or the like, the winch is automatically immobilized.
The operator of these winch systems must pay careful attention to the position of his control lever or the like in order to control movement of a load in a safe and efficient manner. It is particularly important to avoid movement of the lever into the Disconnect position through misjudgment while a load is pulling on the cable since momentum and overtravel may cause an excessive amount of cable to be released, creating unwanted slack, when dropping of the load stops or slows. Diversion of the operator's visual attention in order to guard against this occurrence is undesirable in many cases, particularly in such usages as on a long skidder where the operator must pay attention to controlling the vehicle itself in addition to operating the winch.
In order to guard against inadvertent movement of the control lever into the Free-Spool position, the lever has been heretofore constrained to pivot along a slot in a console which includes an angled section whereby sideward movement is needed before the lever movement can be continued into the Free-Spool position from the adjacent position. While this arrangement accomplishes the objective of alerting the operator when the lever approaches the Free-Spool position, it also undesirable complicates lever manipulations and delays shifting into the Free-Spool mode at times when fast action may be required.